Naslov
Planktonic Foraminiferal Biostratigraphy and Palaoecology of the Oligocene in the North Adriatic Sea (Croatia)

Autori
Hernitz Kučenjak, Morana ; Premec-Fuček, Vlasta ; Slavković, Renata

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Forams 2010 - International Symposium on Foraminifera, Abstracts Volume with program / Organizing Committee in Bonn - Bon : Friedrich-Wilhelms-Universität Bonn, 2010

Skup
Forams 2010 - International Symposium on Foraminifera

Mjesto i datum
Bonn, Njemačka, 05.09.2010. - 10.09.2010

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
biostratigraphy; Oligocene; planktonic foraminifera; North Adriatic Sea

Sažetak
In the North Adriatic Sea very well preserved Oligocene planktonic foraminifera assemblages have been observed. The detailed biostratigraphic study was based on samples from drill cuttings and cored intervals from the three deep exploration wells located in the Adriatic Sea on the edge of Adriatic Carbonate platform towards the Venetian basin. Oligocene sediments consist of monotonous silty marls with rare and thin siltstone beds. The basement of area is built up of Upper Eocene sediments. After the Oligocene, sedimentation continued through Lower Miocene. Rich planktonic foraminiferal association with index species enabled identification of six Oligocene biostratigraphic Zones: Pseudohastigerina naguewichiensis – O1, Turborotalia ampliapertura – O2, Globigerina sellii – O3, Globigerina angulisuturalis/Chiloguembelina cubensis – O4, Paragloborotalia opima – O5 and Globigerina ciperoensis – O6. E/O boundary is marked by extinction of Hantkenina and Cribrohantkenina as well as turborotalids of the T. cerroazulensis group. Planktonic assemblages in the Zone O1 are characterized by increased proportions of non-spinose deep-water globigerinid forms of Dentoglobigerina and Globoquadrina, while small planktonic forms adapted to life in surface water layer are rare. In the Zone O2, beside previously mentioned taxa, Turborotalia ampliapertura and T. increbescens prevail in the assemblages. Catapsydrax, Globorotaloides, Tenuitella, Subbotina and Chiloguembelina are also well presented in O2 Zone. In the next Zone (O3), continuing trend of moderate cooling is evident by presence of Catapsydrax, Globorotaloides, Tenuitella, as well as Chiloguembelina and Paragloborotalia nana. Specimens of Dentoglobigerina and Globoquadrina are still abundant. Appearance of small spinose planktonic foraminifera of G. ciperoensis group and Globoturborotalita in Zone O4 indicate warmer water conditions. Boundary between upper and lower Oligocene was determined based on high common occurrence (HCO) of C. cubensis. In the Zone O5 warm water indicators, spinose species of G. ciperoensis group and Globoturborotalita become more frequent, whereas abundance of large globigerinids, such as Dentoglobigerina and Globoquadrina decrease. The Zone O6 is characterized by considerable decrease of diversity in northern Adriatic area. Diversity and morphological features of planktonic foraminiferal tests imply a general cooling trend which began at the Eocene/Oligocen boundary. Increase of the warm water species during the Upper Oligocene indicates a further paleooceanographic changes and warmer climate conditions.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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